@article{ref1,
title="Epidemiological studies",
journal="WHO Regional Publications European Series",
year="1992",
author="Kilbourne, E. M. and Posada de la Paz, M. and Abaitua Borda, I.",
volume="42",
number="",
pages="5-25",
abstract="<p>[Abstract unavailable]</p><p>Language: en</p>",
language="en",
issn="0378-2255",
doi="",
url="http://dx.doi.org/"
}